At present, a small-volume medium-voltage switch cabinet in a 3.6˜40.5 kV power system is a gas-filled cabinet filled with SF6 (sulfur hexafluoride) gas as an insulating medium. However, under conditions of high power electric arc, spark discharge and corona discharge, the SF6 gas will decompose and dissociate various substances, and the decomposed and dissociated substances will react with oxygen, water, metal and insulating materials to generate some toxic matters. For a long time, since the gas-filled cabinet filled with SF6 gas as an insulating medium cannot be absolutely sealed, a phenomenon that the gas leaks necessarily exists. The following problems accordingly occur:
day by day, leakage of the toxic gas generated from the decomposition of SF6 gas will harm operators and the ambient environment;
there are six greenhouse gases that are discharged from human activities, and SF6 gas is one of them, with a lifespan of 3400 years and thus has a potential threat to the “greenhouse effect”;
when the SF6 gas leaks to a certain ratio without charging in time and thus results in inadequacy of the insulating intensity, it will damage devices and cause safety accidents;
a recycling apparatus for the SF6 gas is so expensive and it's popularity is limited. In addition, it's utilization is poor and is usually used in device mounting and repairing only. Some of middle or small enterprises are not equipped with the SF6 gas recycling apparatus at all, leading to environment and safety risks.
Presently, there is no SF6 gas recycling apparatus that can regenerate the SF6 gas, so recycling of SF6 gas is very poor. Exhaust gas is let out to air directly or only through simply filtering and adsorbing.
So, in the future medium-voltage electrical industry, it appears that an electrical appliance with less or no SF6 gas is a developing trend of the medium-voltage electrical manufacturing industry.